[Postactivation changes in the ultrastructure of motor neurons].

The prolonged high-frequency synaptic activation of the frog spinal motoneurons suppressing their firing, leads to an increase in the size of synapses and to a considerable shift in their ultrastructure. Restoration of the functional and morphological alterations in the cells after cessation of their rhythmical activation proceeds with different speed: the restoration of neurons' ability to generate synaptic and spike potentials in response to testing stimulation of afferents occurs much earlier than the restoration of the cells' ultrastructure and size. Neurons with obviously changed ultrastructure of soma and synaptic apparatus are capable of generating synaptic and spike potentials in response to stimulation.

[Effect of a ginseng tissue culture preparation on morphofunctional changes in motor neurons upon activation].

Irritation for 10 min of the posterior spinal root in the frog Rana temporaria (electrical stimulation 50 imp/sec, threshold power 4) results in decreasing size of the motoneurons and their nuclei and in appearing pycnomorphous type of neurons. Simultaneously, peculiar changes in cellular ultrastructure connected with inhibition of protein synthesis are observed. When the ginseng preparation is administered to intact animals, an increased excitability of the spinal centers, as well as increasing volume of the motoneuronal nuclei and certain ultrastructural shifts demonstrating activation of protein synthesis and cellular energy are observed.

[The influence of synaptic processes on changes in neuronal structure].

Reactions of the spinal motoneurons to the afferent inflow were different in frogs: some neurons generated spike potentials during 10-min rhythmic stimulation (1/sec) of afferents, other neurons were switched on and off. The motoneurons and their synapses increased in size, their cytoplasmic matrix became lighter and ribosoms deteriorated. Antidromic activation did not entail modofocation of size or color of the cells.